平行部を有するダンベル型試験片による超音波疲労試験

概要

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Dumbbell-type specimens having a straight part was used in ultrasonic fatigue testing for high-strength steel in order to enlarge risk volumes. In this case, the stress distribution in the straight part was almost uniform in the axial direction. The steel used was low-temperature-tempered SCM440 low-alloy steel and the steel showed fish-eye fracture originating mostly from an Al_2O_3 inclusion. The ultrasonic fatigue testing results were compared with the conventional servo-hydraulic fatigue testing. The two kinds of fatigue testing results showed good agreements in case of fish-eye fracture. This agreements supported the validity of the ultrasonic fatigue testing with specimens having a straight part in the gigacycle fatigue tests ending in fish-eye fracture. Moreover, the ultrasonic fatigue testing were conducted also with specimens without a straight part to confirm the effects of the risk volumes. In comparing those ultrasonic fatigue testing results, the effects of the risk volumes were cleary observed, i.e. the result with larger risk volumes showed lower fatigue strengths due to presence of a larger inclusion at the fish-eye fracture origin.
一般社団法人日本機械学会の論文
2007-08-25